Add redis-cli support for diskless replication (CAPA EOF)

when setting repl-diskless-sync yes, and sending SYNC.
redis-cli needs to be able to understand the EOF marker protocol
in order to be able to skip or download the rdb file

src/redis-cli.c

@@ -1793,9 +1793,31 @@ static void latencyDistMode(void) {
  * Slave mode
  *--------------------------------------------------------------------------- */
 
+#define RDB_EOF_MARK_SIZE 40
+
+void sendReplconf(const char* arg1, const char* arg2) {
+    printf("sending REPLCONF %s %s\n", arg1, arg2);
+    redisReply *reply = redisCommand(context, "REPLCONF %s %s", arg1, arg2);
+
+    /* Handle any error conditions */
+    if(reply == NULL) {
+        fprintf(stderr, "\nI/O error\n");
+        exit(1);
+    } else if(reply->type == REDIS_REPLY_ERROR) {
+        fprintf(stderr, "REPLCONF %s error: %s\n", arg1, reply->str);
+        /* non fatal, old versions may not support it */
+    }
+    freeReplyObject(reply);
+}
+
+void sendCapa() {
+    sendReplconf("capa", "eof");
+}
+
 /* Sends SYNC and reads the number of bytes in the payload. Used both by
- * slaveMode() and getRDB(). */
+ * slaveMode() and getRDB().
-unsigned long long sendSync(int fd) {
+ * returns 0 in case an EOF marker is used. */
+unsigned long long sendSync(int fd, char *out_eof) {
     /* To start we need to send the SYNC command and return the payload.
      * The hiredis client lib does not understand this part of the protocol
      * and we don't want to mess with its buffers, so everything is performed
@@ -1825,17 +1847,33 @@ unsigned long long sendSync(int fd) {
         printf("SYNC with master failed: %s\n", buf);
         exit(1);
     }
+    if (strncmp(buf+1,"EOF:",4) == 0 && strlen(buf+5) >= RDB_EOF_MARK_SIZE) {
+        memcpy(out_eof, buf+5, RDB_EOF_MARK_SIZE);
+        return 0;
+    }
     return strtoull(buf+1,NULL,10);
 }
 
 static void slaveMode(void) {
     int fd = context->fd;
-    unsigned long long payload = sendSync(fd);
+    static char eofmark[RDB_EOF_MARK_SIZE];
+    static char lastbytes[RDB_EOF_MARK_SIZE];
+    static int usemark = 0;
+    unsigned long long payload = sendSync(fd, eofmark);
     char buf[1024];
     int original_output = config.output;
 
-    fprintf(stderr,"SYNC with master, discarding %llu "
+    if (payload == 0) {
-                   "bytes of bulk transfer...\n", payload);
+        payload = ULLONG_MAX;
+        memset(lastbytes,0,RDB_EOF_MARK_SIZE);
+        usemark = 1;
+        fprintf(stderr,"SYNC with master, discarding "
+                       "bytes of bulk transfer until EOF marker...\n");
+    } else {
+        fprintf(stderr,"SYNC with master, discarding %llu "
+                       "bytes of bulk transfer...\n", payload);
+    }
+
 
     /* Discard the payload. */
     while(payload) {
@@ -1847,8 +1885,29 @@ static void slaveMode(void) {
             exit(1);
         }
         payload -= nread;
+
+        if (usemark) {
+            /* Update the last bytes array, and check if it matches our delimiter.*/
+            if (nread >= RDB_EOF_MARK_SIZE) {
+                memcpy(lastbytes,buf+nread-RDB_EOF_MARK_SIZE,RDB_EOF_MARK_SIZE);
+            } else {
+                int rem = RDB_EOF_MARK_SIZE-nread;
+                memmove(lastbytes,lastbytes+nread,rem);
+                memcpy(lastbytes+rem,buf,nread);
+            }
+            if (memcmp(lastbytes,eofmark,RDB_EOF_MARK_SIZE) == 0)
+                break;
+        }
     }
-    fprintf(stderr,"SYNC done. Logging commands from master.\n");
+
+    if (usemark) {
+        unsigned long long offset = ULLONG_MAX - payload;
+        fprintf(stderr,"SYNC done after %llu bytes. Logging commands from master.\n", offset);
+        /* put the slave online */
+        sleep(1);
+        sendReplconf("ACK", "0");
+    } else
+        fprintf(stderr,"SYNC done. Logging commands from master.\n");
 
     /* Now we can use hiredis to read the incoming protocol. */
     config.output = OUTPUT_CSV;
@@ -1865,11 +1924,22 @@ static void slaveMode(void) {
 static void getRDB(void) {
     int s = context->fd;
     int fd;
-    unsigned long long payload = sendSync(s);
+    static char eofmark[RDB_EOF_MARK_SIZE];
+    static char lastbytes[RDB_EOF_MARK_SIZE];
+    static int usemark = 0;
+    unsigned long long payload = sendSync(s, eofmark);
     char buf[4096];
 
-    fprintf(stderr,"SYNC sent to master, writing %llu bytes to '%s'\n",
+    if (payload == 0) {
-        payload, config.rdb_filename);
+        payload = ULLONG_MAX;
+        memset(lastbytes,0,RDB_EOF_MARK_SIZE);
+        usemark = 1;
+        fprintf(stderr,"SYNC sent to master, writing bytes of bulk transfer until EOF marker to '%s'\n",
+            config.rdb_filename);
+    } else {
+        fprintf(stderr,"SYNC sent to master, writing %llu bytes to '%s'\n",
+            payload, config.rdb_filename);
+    }
 
     /* Write to file. */
     if (!strcmp(config.rdb_filename,"-")) {
@@ -1898,11 +1968,31 @@ static void getRDB(void) {
             exit(1);
         }
         payload -= nread;
+
+        if (usemark) {
+            /* Update the last bytes array, and check if it matches our delimiter.*/
+            if (nread >= RDB_EOF_MARK_SIZE) {
+                memcpy(lastbytes,buf+nread-RDB_EOF_MARK_SIZE,RDB_EOF_MARK_SIZE);
+            } else {
+                int rem = RDB_EOF_MARK_SIZE-nread;
+                memmove(lastbytes,lastbytes+nread,rem);
+                memcpy(lastbytes+rem,buf,nread);
+            }
+            if (memcmp(lastbytes,eofmark,RDB_EOF_MARK_SIZE) == 0)
+                break;
+        }
+    }
+    if (usemark) {
+        payload = ULLONG_MAX - payload - RDB_EOF_MARK_SIZE;
+        if (ftruncate(fd, payload) == -1)
+            fprintf(stderr,"ftruncate failed: %s.\n", strerror(errno));
+        fprintf(stderr,"Transfer finished with success after %llu bytes\n", payload);
+    } else {
+        fprintf(stderr,"Transfer finished with success.\n");
     }
     close(s); /* Close the file descriptor ASAP as fsync() may take time. */
     fsync(fd);
     close(fd);
-    fprintf(stderr,"Transfer finished with success.\n");
     exit(0);
 }
 
@@ -2893,12 +2983,14 @@ int main(int argc, char **argv) {
     /* Slave mode */
     if (config.slave_mode) {
         if (cliConnect(0) == REDIS_ERR) exit(1);
+        sendCapa();
         slaveMode();
     }
 
     /* Get RDB mode. */
     if (config.getrdb_mode) {
         if (cliConnect(0) == REDIS_ERR) exit(1);
+        sendCapa();
         getRDB();
     }